关于copy
NSMutableArray* a = [NSMutableArray arrayWithObjects:@"123",@"345", nil];
NSMutableArray* b = [NSMutableArray arrayWithObjects:@"xyz",@"abc", nil];
NSArray *c = [NSArray arrayWithObjects:a, b, nil];
NSArray *d = [c copy];
for (NSArray* arr in d) {
for (NSString* s in arr) {
NSLog(@"element: %@", s);
}
}
a[0] = @"haha";
for (NSArray* arr in d) {
for (NSString* s in arr) {
NSLog(@"element: %@", s);
}
}
结果:
2015-07-02 13:53:00.112 Test[15564:327797] element: 123
2015-07-02 13:53:00.112 Test[15564:327797] element: 345
2015-07-02 13:53:00.112 Test[15564:327797] element: xyz
2015-07-02 13:53:00.112 Test[15564:327797] element: abc
2015-07-02 13:53:00.112 Test[15564:327797] element: haha
2015-07-02 13:53:00.112 Test[15564:327797] element: 345
2015-07-02 13:53:00.112 Test[15564:327797] element: xyz
2015-07-02 13:53:00.113 Test[15564:327797] element: abc
******************************************
NSMutableArray* a = [NSMutableArray arrayWithObjects:@"123",@"345", nil];
NSMutableArray* b = [NSMutableArray arrayWithObjects:@"xyz",@"abc", nil];
NSArray *c = [NSArray arrayWithObjects:a, b, nil];
// SEE the difference.
NSArray *d = [c copyDeeply];
for (NSArray* arr in d) {
for (NSString* s in arr) {
NSLog(@"element: %@", s);
}
}
a[0] = @"haha";
for (NSArray* arr in d) {
for (NSString* s in arr) {
NSLog(@"element: %@", s);
}
}
结果:
2015-07-02 13:53:47.111 Test[15596:328543] element: 123
2015-07-02 13:53:47.112 Test[15596:328543] element: 345
2015-07-02 13:53:47.112 Test[15596:328543] element: xyz
2015-07-02 13:53:47.112 Test[15596:328543] element: abc
2015-07-02 13:53:47.112 Test[15596:328543] element: 123
2015-07-02 13:53:47.112 Test[15596:328543] element: 345
2015-07-02 13:53:47.112 Test[15596:328543] element: xyz
2015-07-02 13:53:47.112 Test[15596:328543] element: abc
copy只做第一级的深拷贝。 如果array里面存的是指针，它就会把指针值做深拷贝，等于是后面的数组跟前面的数组，存的指针值是一样的，但是指针指向的内容不做深拷贝，所以改了指针指向的内容，会同时影响两个数组。